CN 2876787 Y discloses a method for measuring a choke current. Specifically, the document relates to a current sensor for measuring a current through a conductor. The conductor is wound onto a C-shaped core, a Hall sensor which is mounted on a printed circuit board being arranged in the air gap in the C-shaped core. The current through the conductor magnetizes the core. The magnetic flux through the core continues through the Hall sensor on the printed circuit board. The voltage which is generated by the magnetic field or by the magnetic flux density of the magnetic field in the Hall sensor is a measure of the magnetic flux density and therefore of the current through the conductor.
WO 2011/029018 A2 discloses measurement of the current through a power line. To this end, the power line is surrounded by a C-shaped core onto which a compensation coil is wound and in the air gap of which a Hall sensor is arranged. A compensation current through the coil is regulated in such a way that the magnetic flux which is induced in the core by the current through the power line and detected by the Hall sensor disappears. The compensation current which is regulated in such a way is a direct measure of the current flowing in the power line.
DE 103 17 215 A1 discloses a method for determining the quality of permanent magnets. The permanent magnet is moved relative to a receiving sensor. In the process, the actual magnetization is ascertained in the form of a field strength curve. Any fault in the permanent magnet in its operating range is determined by comparing the field strength curve with an ideal curve.
DE 10 2011 000 980 A1 discloses a choke with dynamic premagnetization. The choke has a choke winding, a core, a permanent magnet for premagnetizing the core, and a magnetization device for setting the desired magnetization of the permanent magnet. The magnetization device can be used to match the premagnetization of the core to the operating conditions of the choke. A magnetization detection device which detects the magnetization of the permanent magnet of the choke is also provided. This magnetization detection apparatus monitors the time profile of a choke current through the choke winding for signs of undesired saturation of the core. It is therefore possible to establish whether the magnetization of the permanent magnet has decreased or is no longer suitable for other reasons.
The typical objective of a magnetic bias of a choke is to extend the active operating range of the choke, in which magnetic saturation of the core of the choke does not occur, for a choke current which flows only in one direction.
DE 10 2010 062 237 A1 discloses a method for calibrating a magnetic field sensor with a permanent magnet. The method comprises applying a first magnetic field with a first strength to the magnetic field sensor and reading out a first response voltage, and also applying a second magnetic field with a second strength to the magnetic field sensor and reading out a second response voltage. Furthermore, the sensitivity of the magnetic field sensor is ascertained on the basis of the difference between the first and the second magnetic field strength and the difference between the first and the second response voltage. The useful field strength of the permanent magnet is then ascertained on the basis of the ascertained sensitivity. In this way, the useful field strength of the permanent magnet is determined during operation of the magnetic field sensor. For a coil, the generated magnetic field is proportional to the current in the coil. Therefore, it is possible to deduce the useful field strength of the permanent magnet by means of a change in the current in the coil and the response voltages which are measured in the process.
JP S62-163974 A discloses a current sensor in which an offset voltage of a Hall element is compensated by means which generate a magnetic auxiliary field. These means comprise an auxiliary coil. At a current, which is to be measured, of zero, the current flowing through the auxiliary coil is set such that the offset voltage is changed to zero.